Test that PEM_BUFSIZE is passed into pem_password_cb

When pem_password_cb is used from SSL_CTX, its size
parameter should be equal to PEM_BUFSIZE.

Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/17320)

test/certs/leaf-encrypted.key

@@ -0,0 +1,30 @@
+-----BEGIN ENCRYPTED PRIVATE KEY-----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+-----END ENCRYPTED PRIVATE KEY-----

test/sslapitest.c

@@ -672,15 +672,27 @@ end:
     return ret;
 }
 
+static int get_password_cb(char *buf, int size, int rw_flag, void *userdata)
+{
+    static const char pass[] = "testpass";
+
+    if (!TEST_int_eq(size, PEM_BUFSIZE))
+        return -1;
+
+    memcpy(buf, pass, sizeof(pass) - 1);
+    return sizeof(pass) - 1;
+}
+
 static int test_ssl_ctx_build_cert_chain(void)
 {
     int ret = 0;
     SSL_CTX *ctx = NULL;
-    char *skey = test_mk_file_path(certsdir, "leaf.key");
+    char *skey = test_mk_file_path(certsdir, "leaf-encrypted.key");
     char *leaf_chain = test_mk_file_path(certsdir, "leaf-chain.pem");
 
     if (!TEST_ptr(ctx = SSL_CTX_new_ex(libctx, NULL, TLS_server_method())))
         goto end;
+    SSL_CTX_set_default_passwd_cb(ctx, get_password_cb);
     /* leaf_chain contains leaf + subinterCA + interCA + rootCA */
     if (!TEST_int_eq(SSL_CTX_use_certificate_chain_file(ctx, leaf_chain), 1)
         || !TEST_int_eq(SSL_CTX_use_PrivateKey_file(ctx, skey,